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At least 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Literature Review of Recycling Polypropylene and Polyamide 12 Powders for Selective Laser Sintering

Additive manufacturing (AM) is the creation of three-dimensional parts by adding material layer-by-layer based on two dimensional “slices” of a CAD file, without molds or tooling. AM has broken the relationship between part complexity and manufacturing cost. As a general rule, for conventional manufacturing, the more complex the part produced, the more costly its manufacturing. For example, in the production of a bracket for a satellite, moving from conventional manufacturing to AM allowed the part to be consolidated from 4 parts to just one, as well as reducing the weight of the part by 35%. A further benefit, AM can be more cost effective for small lot sizes. To illustrate, consider a case study of white board marker caps presented by Klahn et al. The cost to produce 1,000 units of a new design using SLS was about an order of magnitude lower than conventional manufacturing, as shown in Figure 1.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Deformation and damage of sintered low-porosity aluminum under planar impact: microstructures and mechanisms

In this paper, plate impact experiments are conducted to study compaction and spallation of 5% porosity aluminum. Free surface velocity histories, the Hugoniot elastic limit (HEL), and spall strengths are obtained at different peak stresses and pulse durations. Scanning electron microscopy, electron backscatter diffraction, and X-ray computed tomography are used to characterize 2D and 3D microstructures. 3D void topology analyses yield rich information on size distribution, shape, orientation, and connectivity of voids. HEL decreases/increases with sample thickness/impact velocity and approaches saturation. Its tensile strength increases with increasing peak stress and shock-induced densification. With the enhanced compaction under increasing impact velocities, spall damage modes change from growth of original voids to inter-particle crack propagation and to “random” nucleation of new voids. Such a change in damage mechanism also gives rise to a distinct decrease in damage extent at high impact velocities. Finally, compaction induces strain localizations around the original voids, while subsequent tension results in grain refinement, and shear deformation zones between staggered cracks.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Correlation Between Structural, Magnetic and Dielectric Properties of Microwave Sintered Ni-Zn-Al Nanoferrites

A series of diamagnetic aluminum (Al{sup 3+}) substituted Ni-Zn Nanoferrites have been synthesized using sol-gel auto combustion route. Structural, magnetic, and dielectric properties were systematically studied and reported with respect to Al{sup 3+} substitution in host Fe{sup 3+} ions. X-ray diffraction (XRD) and infrared spectroscopy (IR) measurements confirm the presence of Al{sup 3+} ions at both A and B sites. Cation distribution proposed from XRD and IR correlates with magnetic and dielectric results. It is observed that Al{sup 3+} ions are distributed in to tetrahedral and octahedral sub-lattices. The saturation magnetization varies between 58.5 and 44.2 emu/g with increasing Al{sup 3+} substitution. This decrease in magnetization is ascribed to presence of the non-collinear spin (canted spin) structure in octahedral sub-lattice. Dielectric constant decreased and a significant improvement in AC resistivity is observed with Al{sup 3+} substitution. The observed variations are accounted on the basis of cation distribution in spinel ferrite.

77 NANOSCIENCE AND NANOTECHNOLOGY↗